I don't see it as intractable. We already have two ways to do that at scale. One is proven (the fission reactors), the other one is proven but not in an actual fusion reactor yet. Iter will have such a blanket for tritium breeding.
Intractable in my mind sounds more like something that you don't know how to even start.
Intractable in my mind sounds more like something that you don't know how to even start.